Aqueous printing inks which use a water-dispersible or dissipatable polyester as, for example, a pigment carrier or binder, are known in the art as taught in, for example, U.S. Pat. Nos. 4,883,714; 4,847,316; 4,704,309; and 4,738,785. The polyesters described in these prior art patents require the presence of a poly(ethylene glycol) moiety (the definition of which includes diethylene glycol), as well as a metal sulfonate moiety attached to an aromatic nucleus. Inks containing such a polyester have many desirable properties such as good adhesion to a variety of substrates and a wide viscosity range.
However, because of the wide range of printing conditions and substrates used in the printing industry, a given ink formulation can have ideal properties for some applications and poor properties for other applications. For example, it has been shown that water resistance of certain of such aqueous inks on substrates such as aluminum can depend upon the particular species of polyester material employed (see Ser. No. 07/513,724, filed even date herewith in the names of Linda Jane Adams and George J. O'Neill). While the inks containing these particular polyesters have excellent water resistance when printed onto aluminum, we have unexpectedly discovered that these same inks have poor freeze-thaw stability. In order to solve the problem of poor freeze-thaw stability of these inks, we have incorporated propylene glycol into these inks in amounts and under conditions as hereinafter described.